Lawn Chemical Sprayer Calibration

Applying foliar applications whether it’s a Herbicide, Insecticide, Fungicide or even a liquid like Special Fex Fertiliser is something we all at some point need to do. However, it isn’t that easy to do if you don’t know what your doing, yet very easy with practice.  The key to any good foliar application is evenness and consistency, all substances have a recommended rate that needs to be applied over a given area, this is NOT the mixed volume rate.  Often a mixed maximum and minimum volume rate is given with a spray nozzle size to adjust the coarseness of the spray, this is normally associated with the type of substance being applied and its targeted area.  Such as the leaf, a lower volume with a finer mist is recommended, where as targeting the base or “crown” of a plant and soil requires a courser higher volume application, but not to be confused a hose on soil drench.

So, what I recommend is to measure out a known area.  For example, say 5mx10m (50m2) on your driveway, or somewhere with enough room and with a surface that you can clearly see your spray pattern and coverage. Fill your sprayer with water with a known amount of water or to specific point and note it. For example, 10lts.  With the sprayer on your driveway on a still day (always try to spray on a still cooler time of day).  Walk at a slow steady pace up and down in an even pattern until the area has an even coverage it must be comfortable for you, so it is repeatable.  Look at the volume you’ve gone through and note it, I recommend repeating this process 2 or 3 times. This will give you more of an accurate indication of how much volume you apply over this area.  Everyone is different, every sprayer is different and its unique to you, but you MUST know.  If you do interchange spray nozzles then this process needs to be done for each nozzle, in which the pattern and movement is the same just the delivery is different.


You also MUST know the area of your lawn, no guessing! there are great apps available to assist you with this if you have trouble (I use “Cam to Plan”).  Then once you know apply this rate to your area of lawn. You get great results with professional products, but it’s not forgiving.  Now that you know your volume of water applied over a known area this is your constant.  All spray on products have a rate per 100m2 or per hectare (divide by 100 to get 100m2).   Apply this to how much you add to your sprayer tank and the required volume of water to cover your area. So, in this case for example.  I spray 10lt per 100m2, I would fill the sprayer with 5-7 ltrs of water.  Add the required amount of product to the tank, add your surfactant which is like a sticky agent to help spray adhesion to the leaf if as this is often recommended on labels.  It is preferable to use a dedicated “Non-ionic” product, if you don’t have one a squirt of detergent will suffice for liquid fertilisers only, I don’t recommend detergent for herbicides, insecticides and fungicides “Ionic” products can change the chemical makeup of the spray.  Top up the sprayer to the 10lt mark agitating the mix. Make sure you apply all of you budgeted mix for this area.  Normally it is only a foliar spray so only the fine mist over the leaf is all you want need unless you are applying a coarse spray to the crown as mentioned.

With handling any sprays, always read the label wear appropriate Personal Protective Equipment and be safe people.  Enjoy the results, a handy tip is to purchase Big Foot marking dye to help with your coverage.


Cheers Addicts!